I have a line which has points (x1,y1) and (x2,y2). I wanted to attach a Button to it, it should align with the line by rotating based on the line segment points. I need some help in calculating the rotation angle for the Button.

Tag: math,javafx,geometry,coordinates

I have a line which has points (x1,y1) and (x2,y2). I wanted to attach a Button to it, it should align with the line by rotating based on the line segment points. I need some help in calculating the rotation angle for the Button.

You can use the `Math.atan2(dy, dx)`

to get the angle `theta`

from the conversion of rectangular coordinates (x, y) to polar coordinates (r, theta). Later use it to convert it to degrees.

```
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.scene.shape.Line;
import javafx.stage.Stage;
public class Main extends Application {
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage primaryStage) throws Exception {
double startX = 100;
double endX = 250;
double startY = 150;
double endY = 250;
Line line = new Line(startX, startY, endX, endY);
Button button = new Button("Button");
double rad = Math.atan2(endY - startY, endX - startX);
double degree = rad * 180/Math.PI;
button.setRotate(degree);
StackPane box = new StackPane(line, button);
Scene scene = new Scene(box, 500, 500);
primaryStage.setScene(scene);
primaryStage.show();
}
}
```

**OutPut**

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